Heuristic Approach to Incorporate Timesharing Schemes in Multiperiod Heat Exchanger Network Designs

Abstract

Heat exchanger network (HEN) synthesis has been widely recognized as an effective design method for significant energy saving in industrial processes. Although traditionally its sole objective is to minimize the total annual cost, there are additional implementation issues which must be addressed in realistic multiperiod applications. In particular, if a conventional programming-based procedure is adopted for generating the optimal HEN structure, each embedded match inevitably calls for different heat-transfer areas in different periods. Since the usual practice is to select the largest unit, its operation in one (or more) period may be grossly inefficient because the corresponding overdesign level is simply too high. To circumvent this drawback, a modified mathematical model and a set of timesharing heuristics have been developed in this work to generate practical network configurations that can handle all heat duties. On the basis of the extensive case studies performed so far, it can be observed that this proposed approach is especially effective for multiperiod HEN design problems in which the process conditions vary significantly.